IBAUHAMBURG CentralCone BlendingSilo · to flow together by funneling (3) flows and thus merging with one another. The gravity flow in the funnels produces the blending effect. The

IBAU HAMBURG

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IBAU HAMBURGCentral ConeBlending Silo

The original IBAU HAMBURG Central cone blending silo

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The constructionof theIBAU HAMBURGCentral coneblending silo

The blending silo issimultaneously used for acontinuous blendingprocess as well as for rawmeal storage.The feeding of the silotakes place via a noveltype of paralleldistributor (1) ensuringa controlled build-upof the different materiallayers.Homogenizing of the rawmeal is achieved bycausing the layers of dif-ferent CaCO3 content (2)to flow together byfunneling (3) flows andthus merging with oneanother.The gravity flow inthe funnels produces theblending effect.The bottom of the silois divided into aerationsections (9).Each section has a flowcontrol gate and an airvalve assigned to it.Blowers are available foraerating the silo bottom.As a result, funnels areformed simultaneouslydeveloping relativelyslowly from the silo bot-tom to the upper surfaceof the stored material.The controlled funnelformation process avoidsthat the fresh raw mealwhich has just been fedinto the silo cannot rushstraight through to thesilo outlet. The powerconsumption amountsto 0.1 - 0.3 KWh/tof raw mix.

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1 Parallel distributor

2 Material layers

3 Funnel

4 The originalIBAU Central cone

5 The IBAUFlow control gate

6 Annular aerationbottom

7 Metering bin

8 The IBAUFlow control gate

9 Aeration sectionswith open-typefluidslides

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Raw meal silo for Dyckerhoff Cement works, Lengerich, Germany

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View into the original IBAU Central

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cone silo with aeration sections

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Material distribution during feeding

Parallel distributor on the silo top

Advantages of theIBAU Central coneblending silos:IBAU Central coneblending silos reduce thechemical and physicalmaterial variations in flu-idizable products such ascement raw meal downto values within the mea-suring tolerance range.

The silos are operated ina continuous flow-through mode, also serv-ing the purpose of rawmeal storage. The blend-ing process is based onexperience in statistical

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Funnel creation during the discharge process

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Aeration section with silo outlet

central bin is used tocollect the differentmaterial flows. Thedesign of the roller open-ing is directly connectedto the linear function ofthe flow control gate.

With this type of gate,the material flow can bemetered very accurately.This flow can be con-trolled via belt weigheror flow-through meter.

The blending effect isdefined by the ratio ofa standard deviationof CaCO3 at the silo inletand the silo outlet. The

degree of the blendingeffect depends on varia-tions in the layer struc-ture, size of the silo inrelation to throughputvolume, filling height ofthe silo and the numberof silo units involved.

Depending on thesefactors, blending resultsof 5:1 up to 15:1 canbe achieved.

The specific powerconsumption amountsto 0.1 - 0.3 kWh/t. Forthe aeration of the silo,single-stage rotary pistonblowers are used.

During the dischargeprocess, the flow controlgates which are installedon the inner circumfer-ence of the central blend-ing silo cone, are activat-ed in combination withthe adjacent aerationsection. A programmedcontroller will start theoperation in an alternat-ing mode.

During the dischargeprocess a funnel flow iscreated, the layer struc-ture is broken up and anactive material exchangetakes place resulting inmaterial blending. The

material distribution. Asmany separate materiallayers as possible arebuilt up horizontally inthe silo.

Feeding of the centralcone blending silo iscarried out via a paralleldistributor which distrib-utes fluidized raw mealevenly over the entiresilo cross-section. Theblending process takesplace during dischargeoperation. The centralcone diverts the gravityflow of the stored prod-uct outwards to the annu-lar aeration bottom.

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Material flow from an active section to the IBAU Flow control gate

Simultaneous aeration of two sections

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Airslide system at the silo bottom

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Material discharge from the complete aeration area

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Silo discharge via IBAU Flow control gate

tling the complete unit.After having taken offone of the side plates theroller can be removed.

The gasket is thenaccessible and can bereplaced if required.Reassembly is carried outin reverse order.

Controlled weigherfeedingequipment

Raw meal meteringequipment plays an im-portant role in the cementproduction. Prior tofeeding the preheater ofthe kiln, raw meal ex-tracted from a blending orstorage silo is continuous-ly weighed by means offlow meters. Often, aweighing prebin installedon load cells is used. Thisprebin allows the controlof the weighing systemand makes it possible to

goods with reproducibleresults. They requirepractically no mainte-nance. However, evengood things are subject towear after many years ofgood service under severeconditions.

Different designs of otherflow control gates maymake it necessary todisassemble the completeunit. However, thanksto the design of theIBAU Flow control gate,a complete disassemblybecomes unnecessary.Maintenance can be car-ried out without disman-

The IBAUFlow control gateType IBN

The IBAU Flow controlgate type IBN shows alladvantages andfeatures of the worldwiderenowned IBAUFlow control gate, whichhas been installed morethan 500,000 times.

The variations of thebasic type with differentactuators have in com-mon the extremely highaccuracy of a controlledflow of pulverized bulk

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keep a constant levelwhich in turn ensures apermanent height of rawmeal above the aeratedbottom.

Flow control gates moni-tor the flow of raw mealbetween the prebin andthe weighing equipment.For this type of appli-cation pneumatic operatedflow control gates withelectro pneumatic controldevice are used. Thematerial flow is controlledby a signal exchange withthe flow meter.

The pneumatic actuatorsoperate according to theprinciple of rotary paddlepneumatics without theuse of lever arms, toothedracks and gears. Thisallows the pure torqueto be transferred, with nointerfering side forces act-ing on the square drive.

The actuators, which arecharacterized by a com-pact and weight-savingdesign, require littleor no maintenance. Theactuator device alsocomes equipped withventilation options, en-abling it to be also movedmanually (hand lever).

The flow control gates ofthe stand-by equipmentcan be set via remotecontrol exactly to thecurrent operating positionof the main line.

The figure on the leftillustrates the arrange-ment of a weighingstation with flow meteringequipment.

Cone silooutlet

Weighingprebin

The IBAUFlow controlgate withpneumaticcontroldevice

Stand-byequipment

The IBAU Screw pumpfor preheather feeding

Flowmeteringequipment

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Flow metering equipment

The IBAUFlow control gatewith pneumaticallycontrolled drive

The pneumatic actuatoris designed for the linearcontrol of the materialthroughput quantity.

A further importantfeature is the emergencyshutdown, i. e. the flowcontrol gate is closedpneumatically in case ofa power failure. The set-

point as well as a positionfeedback are carried outby means of a 4-20 mAsignal.

The combination of anydesired type of roller witha pneumatic actuator,connected to an electropneumatic control device,is eminently suitable

for bulk handling, e. g. onthe discharge spouts ofsilos or bins where a lin-early controlled dischargeis required and where, forsafety reasons, thedischarge process mustbe stopped in case of apower failure.

IBAU Flow control gate with pneumatic actuator and control device

Flow control gate with adjustable cross-section

Material flow direction Angular aperture Adjustable cross-section Cross-section projection

Angular aperture

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The IBAUScrew pump

Screw pumps have beenin use for more than fiftyyears for the pneumatictransport of cement, rawmeal, all types of lime,pulverized coal, fly ash,alumina and many otherpulverized materials.

It is a conveying unitwhich is able to feedlarge quantities of suchmaterials into a pneu-matic conveying linepractically without anyblowback of air.

A further advantage ofscrew pumps is theircompactness and espe-cially their low overallheight. These low spacerequirements make them

maintenance either.(Air intake filter andchanging of gear oil).Parts of an airlift systemare: The cylindrical airliftbody with aerated bot-tom, the vertical nozzleand conveying pipe, aseparator (when not feed-ing directly a preheater ora small silo). As with allother types of pneumatictransport a dedusting atthe end of the conveyingline is necessary.

A rotary piston bloweror a group of blowerssupply the necessaryoil- free conveying air.

A head of conveyingmaterial forms the air lockagainst atmosphericpressure; in other wordsthe higher to convey thehigher the airlift body.

suitable for confinedlocations. Screw pumpscan operate againstconveying line back pres-sures of up to 2.5 bar.

They are available invarious sizes with capaci-ties ranging from about5 to 500 m3/h.

The IBAU Airlift

An alternative for thepreheater feeding is theIBAU Airlift, whichfacilitates a dust-free ver-tical transport. The airliftdoes not require muchmaintenance as there areno mechanical parts inthe conveying line whichhave to be maintained.A rotary piston blowersupplying the conveyingair does not require much

IBAU Screw pump for material transport to the preheater

IBAU Airlift system forthe material transport

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The IBAUBlending silooperation

The silo feeding has to becarried out continuouslyso that horizontal layerswith equal grading arebuilt.

The layers must havedifferent chemical andphysical compositions,thus being statisticallyindependent fromeach other. The thinnerthe layers with differentcharacteristic concen-trations are, the moreeasily they blend witheach other.

Therefore, it is essentialfor the achievement of ahigh blending effect thatnot only correspondinglyhigh deviations are pre-sent in the layers but thatthey alternate within thesilo inlet as often aspossible. Thus, theremust be a certain period-icity. All of the knownthroughput blending silosproduce more or lessgravity flow profiles,which are also calledblending funnels.

In order to achieve an op-timal blending effect ahigh ratio of material ex-change and a minium silolevel of 70% are required.

Evaluation ofblending quality

Blending and homogeniz-ing can be understood asuniforming of chemicaland physical variations insolid mixtures such ascement raw meal. Con-centration values withinthe mineralogical mix-

tures are used for the eva-luation, e. g. the CaCO3content in weight-% forcement raw meal.

For a quality assuringmixture control it isnecessary to have arepresentative measure-ment for sampling andanalysis. The evaluationof the blending effectis made according to theregulations for the mathe-matic statistic by usingthe standard deviation.

Individual samples aretaken in front of the siloinlet and after the silooutlet every 0,5 to 1 hourand then are analysedaccordingly. Representa-tive test series are gener-ally made over a periodof 24 hours.

Measuring faultsin theanalysis process

The aforementionedvalues of analysis areafflicted with faults as thedevices for the samplingand analysis onlymeasure samples insteadof the effective valuesof an entity.

Therefore, the fault forthe sampling and analysisprocess with the faultstandard deviation,indicated with „SP+An“,has to be deducted forthe calculation of the ac-tual standard deviations.The measuring faultcan be experimentallyidentified on site.

Within several seconds,several individualsamples are taken and

divided for example into10 test portions. Theneach single test portion isanalysed and thestandard deviation isidentified from the resultswhich then can be usedas SP+An.

For the homogeneityassessment, generallythe concentration degreeof the biggest massfraction being present incement raw meal is taken,such as calcium carbo-nate content, CaCO3, witha weight proportion ofapproximately 70 - 80%.

Graphs indicating data

CaCO3 input deviation (black line)

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Blending effect

The blending effect is defined by the followingrelation:

SEF = Standard deviation with measuring faultsilo inlet

SAF = Standard deviation with measuring faultsilo outlet

SP+An = Standard deviation of the sampling andanalysing process (measuring fault)

SE = Standard deviation without measuringfault silo inlet

SA = Standard deviation without measuringfault silo outlet

A statement, which is actually more importantfor the material quality, can be made by the outletvariation rectified with the measuring fault:

Example blending effect

The following values have been determined andare applied now:SEF = +/-2,1 % CaCO3SAF = +/-0,3 % CaCO3And SP+An is about +/-0,2 %.The blending effect will be:

MS = 9,4The outlet variation is about:SA = +/-0,223 % CaCO3

For the assessment of the silo plant it generallymakes sense to analyse the process factors, whichare also being used for the raw grinding plant andfor the mixed bed composition. This is either thelimestone factor, the tricalcium silicate (C3S) or thetricalcium aluminate (C3A).

The calculation of these process values is done bymeans of the main oxides CaO, SiO2; Al2O3, Fe2O3.

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taken during test period

CaCO3 output deviation (red line)

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Plant view of Signal Mountain Cement

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Company, Chattanooga, Tennessee, USA

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Cement Australia Railton,

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Tasmania, Australia

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Advantages of theIBAU Central coneblending silos:

1. Very uncomplicatedcivil engineeringconcept dueto a favourable loaddistribution via thecentral cone intothe silo wall

2. Optimized materialaeration and dischargetechnology

3. High operatingreliability thanksto direct processparameter control

4. Easy accessfor inspection andmaintenance

5. High blending effectat a low powerconsumption due torealisation of the massflow principle

The raw meal silofulfils two purposes:

It is used for raw mealstorage, in order to feedthe kiln with raw mealeven during the down-times of the raw mealgrinding plant.

Furthermore, ithomogenises the rawmeal produced by the rawmeal grinding plant, sothat a constant clinkerquality can be generatedin the kiln.

Whereas it is important toeither maintain the homo-geneity which was gener-ated in the previous pro-cess steps or, if therequired level of homo-geneity was not reached,to generate it accordingly. Arabian Cement Company Ltd.,

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Rabigh plant, line 1-4, Saudi-Arabia

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I BAU HAMBURG · Rödingsmarkt 35 · D-20459 Hamburg · PHONE +49 (0) 40 36 13 090FAX +49 (0) 40 36 39 83 · Email: [email protected] · Internet: www.ibauhamburg.de

IBAU HAMBURG – THE STATE OF THE ARTWe have designed and built worldwide about 7.000 large capacity silos, 250 multi-compartment silo plants,2.000 pumps for bulk material transport, 250 power plant equipment, 60 terminals for bulk material mixing,100 marine terminals for cement, 30 shipunloaders for cement, and 20 self-unloading cement carriers

Cement silo installation with bulk loadingin Samalayuca / Mexico

High capacity mixing plantHOLCIM, Antwerp / Belgium

Shipunloader on rubber tyres for ContinentalFlorida Materials, Port Canaveral / USA

Raw meal blending silo,Dyckerhoff Zement / Germany

Coal-fired power plantMehrum / Germany

Cement carrierM.V. GLEN VINE

Documents

IBAUHAMBURG CentralCone BlendingSilo · to flow together by funneling (3) flows and thus merging with one another. The gravity flow in the funnels produces the blending effect. The